Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2005-159047) discloses a gallium nitride-based semiconductor device including a gallium nitride-based semiconductor layer with high crystal quality. The gallium nitride-based semiconductor layer is provided on a primary surface of a gallium nitride support of a semiconductor light-emitting device. The normal line of the primary surface and the C-axis of the gallium nitride support form an angle (referred to as “off angle”) with each other. When the off angle of the gallium nitride support is close to zero, the surface of the gallium nitride-based semiconductor layer has a hexagonal pyramidal morphology, and the off angle is less than 2 degrees.